Inflatable device for use in surgical protocol relating to fixation of bone

ABSTRACT

Systems for treating a bone, e.g. a vertebral body, having an interior volume occupied, at least in part, by cancellous bone provide a first tool, a second tool, and a third tool. The first tool establishes a percutaneous access path to bone. The second tool is sized and configured to be introduced through the percutaneous access path to form a void that occupies less than the interior volume. The third tool places within the void through the percutaneous access path a volume of filling material. Related methods for treating a bone, e.g. a vertebral body, having an interior volume occupied, at least in part, by cancellous bone provide establishing a percutaneous access path to bone. A tool is introduced through the percutaneous access path and manipulated to form a void that occupies less than the interior volume. A volume of filling material is then placed within the void through the percutaneous access path.

RELATED APPLICATIONS

[0001] This application is a divisional of co-pending application Ser.No. 10/411,573, filed Apr. 10, 2003, which is a divisional ofapplication Ser. No. 10/200,674, filed Jul. 22, 2002, which is adivisional of 09/059,796, filed Apr. 13, 1998, now U.S. Pat. No.6,423,083, which is a divisional of application Ser. No. 08/788,786,filed Jan. 23, 1997, now U.S. Pat. No. 6,235,043, which is acontinuation of application Ser. No. 08/188,224, filed on Jan. 26, 1994(now abandoned).

FIELD OF THE INVENTION

[0002] This invention relates to improvements in the surgical treatmentof bone conditions of the human and other animal bone systems and, moreparticularly, to an inflatable balloon-like device for use in treatingsuch bone conditions. Osteoporosis, avascular necrosis and bone cancerare diseases of bone that predispose the bone to fracture or collapse.There are 2 million fractures each year in the United States, of whichabout 1.3 million are caused by osteoporosis. Avascular necrosis andbone cancers are more rare but can cause bone problems that arecurrently poorly addressed.

BACKGROUND OF THE INVENTION

[0003] In U.S. Pat. Nos. 4,969,888 and 5,108,404, an apparatus andmethod are disclosed for the fixation of fractures or other conditionsof human and other animal 5 bone systems, both osteoporotic andnon-osteoporotic. The apparatus and method are especially suitable foruse in the fixation of, but not limited to, vertebral body compressionfractures, Colles fractures and fractures of the proximal humerus.

[0004] The method disclosed in these two patents includes a series ofsteps which a surgeon or health care provider can perform to form acavity in pathological bone (including but not limited to osteoporoticbone, osteoporotic fractured metaphyseal and epiphyseal bone,osteoporotic vertebral bodies, fractured osteoporotic vertebral bodies,fractures of vertebral bodies due to tumors especially round celltumors, avascular necrosis of the epiphyses of long bones, especiallyavascular necrosis of the proximal femur, distal femur and proximalhumerus and defects arising from endocrine conditions).

[0005] The method further includes an incision in the skin (usually oneincision, but a second small incision may also be required if a suctionegress is used) followed by the placement of a guide pin which is passedthrough the soft tissue down to and into the bone.

[0006] The method further includes drilling the bone to be treated toform a cavity or passage in the bone, following which an inflatableballoon-like device is inserted into the cavity or passage and inflated.The inflation of the inflatable device causes a compacting of thecancellous bone and bone marrow against the inner surface of thecortical wall of the bone to further enlarge the cavity or passage. Theinflatable device is then deflated and then is completely removed fromthe bone. A smaller inflatable device (a starter balloon) can be usedinitially, if needed, to initiate the compacting of the bone marrow andto commence the formation of the cavity or passage in the cancellousbone and marrow. After this has occurred, a larger, inflatable device isinserted into the cavity or passage to further compact the bone marrowin all directions.

[0007] A flowable biocompatible filling material, such asmethylmethacrylate cement or a synthetic bone substitute, is thendirected into the cavity or passage and allowed to set to a hardenedcondition to provide structural support for the bone. Following thislatter step, the insertion instruments are removed from the body and theincision in the skin is covered with a bandage.

[0008] While the apparatus and method of the above patents provide anadequate protocol for the fixation of bone, it has been found that thecompacting of the bone marrow and/or the trabecular bone and/orcancellous bone against the inner surface of the cortical wall of thebone to be treated can be significantly improved with the use ofinflatable devices that incorporate additional engineering features notheretofore described and not properly controlled with prior inflatabledevices in such patents. A need has therefore arisen for improvements inthe shape, construction and size of inflatable devices for use with theforegoing apparatus and method, and the present invention satisfies suchneed.

Prior Techniques for the Manufacture of Balloons for In-Patient Use

[0009] A review of the prior art relating to the manufacture of balloonsshows that a fair amount of background information has been amassed inthe formation of guiding catheters which are introduced intocardiovascular systems of patients through the brachial or femoralarteries. However, there is a scarcity of disclosures relating toinflatable devices used in bone, and none for compacting bone marrow invertebral bodies and long bones.

[0010] In a dilatation catheter, the catheter is advanced into a patientuntil a balloon is properly positioned across a lesion to be treated.The balloon is inflated with a radiopaque liquid at pressures above fouratmospheres to compress the plaque of the lesion to thereby dilate thelumen of the artery. The balloon can then be deflated, then removed fromthe artery so that the blood flow can be restored through the dilatedartery.

[0011] A discussion of such catheter usage technique is found andclearly disclosed in U.S. Pat. No. 5,163,989. Other details ofangioplasty catheter procedures, and details of balloons used in suchprocedures can be found in U.S. Pat. Nos. 4,323,071, 4,332,254,4,439,185, 4,168,224, 4,516,672, 4,538,622, 4,554,929, and 4,616,652.

[0012] Extrusions have also been made to form prism shaped balloonsusing molds which require very accurate machining of the interiorsurface thereof to form acceptable balloons for angioplastic catheters.However, this technique of extrusion forms parting lines in the balloonproduct which parting lines are limiting in the sense of providing aweak wall for the balloon itself.

[0013] U.S. Pat. No. 5,163,989 discloses a mold and technique formolding dilatation catheters in which the balloon of the catheter isfree of parting lines. The technique involves inflating a plastic memberof tubular shape so as to press it against the inner molding surfacewhich is heated. Inflatable devices are molded into the desired size andshape, then cooled and deflated to remove it from the mold. The patentstates that, while the balloon of the present invention is especiallysuitable for forming prism-like balloons, it can also be used forforming balloons of a wide variety of sizes and shapes.

[0014] A particular improvement in the catheter art with respect to thispatent, namely U.S. Pat. No. 4,706,670, is the use of a coaxial catheterwith inner and outer tubing formed and reinforced by continuous helicalfilaments. Such filaments cross each other causing the shaft of theballoon to become shorter in length while the moving portion of theshank becomes longer in length. By suitably balancing the lengths andthe angle of the weave of the balloon and moving portions of thefilaments, changes in length can be made to offset each other. Thus, theposition of the inner and outer tubing can be adjusted as needed to keepthe balloon in a desired position in the blood vessel.

[0015] Other disclosures relating to the insertion of inflatable devicesfor treating the skeleton of patients include the following:

[0016] U.S. Pat. No. 4,313,434 relates to the fixation of a long bone byinserting a deflated flexible bladder into a medullary cavity, inflatingthe balloon bladder, sealing the interior of the long bone until healinghas occurred, then removing the bladder and filling the opening throughwhich the bladder emerges from the long bone.

[0017] U.S. Pat. No. 5,102,413 discloses the way in which an inflatablebladder is used to anchor a metal rod for the fixation of a fracturedlong bone.

[0018] Other references which disclose the use of balloons and cementfor anchoring of a prosthesis include U.S. Pat. Nos. 5,147,366,4,892,550, 4,697,584, 4,562,598, and 4,399,814.

[0019] A Dutch patent, NL 901858, discloses a means for fracture repairwith a cement-impregnated bag which is inflated into a preformed cavityand allowed to harden.

[0020] It can be concluded from the foregoing review of the prior artthat there is little or no substantive information on inflatable devicesused to create cavities in bone. It does not teach the shape of theballoon which creates a cavity that best supports the bone whenappropriately filled. It does not teach how to prevent balloons frombeing spherical when inflated, when this is desired. Current medicalballoons can compress bone but are too small and generally have thewrong configuration and are generally not strong enough to accomplishadequate cavity formation in either the vertebral bodies or long bonesof the body.

[0021] U.S. Pat. Nos. 4,969,888 and 5,108,404 disclose a checker-shapedballoon for compressing cancellous bone, but does not provideinformation on how this balloon remains in its shape when inflated.

[0022] Thus, the need continues for an improved inflatable device foruse with pathological bones and the treatment thereof.

SUMMARY OF THE INVENTION

[0023] The present invention is directed to a balloon-like inflatabledevice or balloon for use in carrying out the apparatus and method ofthe above-mentioned U.S. Pat. Nos. 4,969,888 and 5,108,404. Suchinflatable devices, hereinafter sometimes referred to as balloons, haveshapes for compressing cancellous bone and marrow (also known asmedullary bone or trabecular bone) against the inner cortex of boneswhether the bones are fractured or not.

[0024] In particular, the present invention is directed to a balloon foruse in treating a bone predisposed to fracture or to collapse. Theballoon comprises an inflatable, non-expandable balloon body forinsertion into said bone. The body has a predetermined shape and sizewhen substantially inflated sufficient to compress at least a portion ofthe inner cancellous bone to create a cavity in the cancellous bone andto restore the original position of the outer cortical bone, iffractured or collapsed. The balloon body is restrained to create saidpredetermined shape and size so that the fully inflated balloon body isprevented from applying substantial pressure to the inner surface of theouter cortical bone if said bone is unfractured or uncollapsed.

[0025] In addition to the shape of the inflatable device itself, anotheraspect of importance is the construction of the wall or walls of theballoon such that proper inflation the balloon body is achieved toprovide for optimum compression of all the bone marrow. The material ofthe balloon is also desirably chosen so as to be able to fold theballoon so that it can be inserted quickly and easily into a bone usinga guide pin and a cannula, yet can also withstand high pressures wheninflated. The balloon can also include optional ridges or indentationswhich are left in the cavity after the balloon has been removed, toenhance the stability of the filler. Also, the inflatable device can bemade to have an optional, built-in suction catheter. This is used toremove any fat or fluid extruded from the bone during balloon inflationin the bone. Also, the balloon body can be protected from puncture bythe cortical bone or canula by being covered while inside the canulawith an optional protective sleeve of suitable material, such as Kevlaror PET or other polymer or substance that can protect the balloon. Themain purpose of the inflatable device, therefore, is the forming orenlarging of a cavity or passage in a bone, especially in, but notlimited to, vertebral bodies.

[0026] The primary object of the present invention is to provide animproved balloon-like inflatable device for use in carrying out asurgical protocol of cavity formation in bones to enhance the efficiencyof the protocol, to minimize the time prior to performing the surgeryfor which the protocol is designed and to improve the clinical outcome.These balloons approximate the inner shape of the bone they are insideof in order to maximally compress cancellous bone. They have additionaldesign elements to achieve specific clinical goals. Preferably, they aremade of inelastic material and kept in their defined configurations wheninflated, by various restraints, including (but not limited to) use ofinelastic materials in the balloon body, seams in the balloon bodycreated by bonding or fusing separate pieces of material together, or byfusing or bonding together opposing sides of the balloon body, wovenmaterial bonded inside or outside the balloon body, strings or bandsplaced at selected points in the balloon body, and stacking balloons ofsimilar or different sizes or shapes on top of each other by gluing orby heat fusing them together. Optional ridges or indentations created bythe foregoing structures, or added on by bonding additional material,increases stability of the filler. Optional suction devices, preferablyplaced so that if at least one hole is in the lowest point of the cavitybeing formed, will allow the cavity to be cleaned before filling.

[0027] Among the various embodiments of the present invention are thefollowing:

[0028] 1. A doughnut (or torus) shaped balloon with an optional built-insuction catheter to remove fat and other products extruded duringballoon expansion.

[0029] 2. A balloon with a spherical outer shape surrounded by aring-shaped balloon segment for body cavity formation.

[0030] 3. A balloon which is kidney bean shaped in configuration. Such aballoon can be constructed in a single layer, or several layers stackedon top of each other.

[0031] 4. A spherically shaped balloon approximating the size of thehead of the femur (i.e. the proximal femoral epiphysis). Such a ballooncan also be a hemisphere.

[0032] 5. A balloon in the shape of a humpbacked banana or a modifiedpyramid shape approximating the configuration of the distal end of theradius (i.e. the distal radial epiphysis and metaphysis).

[0033] 6. A balloon in the shape of a cylindrical ellipse to approximatethe configuration of either the medial half or the lateral half of theproximal tibial epiphysis. Such a balloon can also be constructed toapproximate the configuration of both halves of the proximal tibialepiphysis.

[0034] 7. A balloon in the shape of sphere on a base to approximate theshape of the proximal humeral epiphysis and metaphysis with a plug tocompress cancellous bone into the diaphysis, sealing it off.

[0035] 8. A balloon device with optional suction device.

[0036] 9. Protective sheaths to act as puncture guard members optionallycovering each balloon inside its catheter.

[0037] The present invention, therefore, provides improved, inflatabledevices for creating or enlarging a cavity or passage in a bone whereinthe devices are inserted into the bone. The configuration of each deviceis defined by the surrounding cortical bone and adjacent internalstructures, and is designed to occupy about 70-90% of the volume of theinside of the bone, although balloons that are as small as about 40% andas large as about 99% are workable for fractures. In certain cases,usually avascular necrosis, the balloon size may be as small as 10% ofthe cancellous bone volume of the area of bone being treated, due to thelocalized nature of the fracture or collapse. The fully expanded sizeand shape of the balloon is limited by additional material in selectedportions of the balloon body whose extra thickness creates a restraintas well as by either internal or external restraints formed in thedevice including, but not limited to, mesh work, a winding or spoolingof material laminated to portions of the balloon body, continuous ornon-continuous strings across the inside held in place at specificlocations by glue inside or by threading them through to the outside andseams in the balloon body created by bonding two pieces of body togetheror by bonding opposing sides of a body through glue or heat. Sphericalportions of balloons may be restrained by using inelastic materials inthe construction of the balloon body, or may be additionally restrainedas just described. The material of the balloon is preferably anon-elastic material, such as polyethylene tetraphthalate (PET), Kevlaror other patented medical balloon materials. It can also be made ofsemi-elastic materials, such as silicone or elastic material such aslatex, if appropriate restraints are incorporated. The restraints can bemade of a flexible, inelastic high tensile strength material including,but not limited, to those described in U.S. Pat. No. 4,706,670. Thethickness of the balloon wall is typically in the range of {fraction(2/100)}ths to {fraction (25/1000)}ths of an inch, or other thicknessesthat can withstand pressures of up to 250-400 psi.

[0038] A primary goal of percutaneous vertebral body augmentation of thepresent invention is to provide a balloon which can create a cavityinside the vertebral body whose configuration is optimal for supportingthe bone. Another important goal is to move the top of the vertebralbody back into place to retain height where possible, however, both ofthese objectives must be achieved without fracturing the cortical wallof the vertebral body. This feature could push vertebral bone toward thespinal cord, a condition which is not to be desired.

[0039] The present invention satisfies these goals through the design ofinflatable devices to be described. Inflating such a device compressesthe calcium-containing soft cancellous bone into a thin shell that linesthe inside of the hard cortical bone creating a large cavity.

[0040] At the same time, the biological components (red blood cells,bone progenitor cells) within the soft bone are pressed out and removedby rinsing during the procedure. The body recreates the shape of theinside of an unfractured vertebral body, but optimally stops atapproximately 70 to 90% of the inner volume. The balloons of the presentinvention are inelastic, so maximally inflating them can only recreatethe predetermined shape and size. However, conventional balloons becomespherical when inflated. Spherical shapes will not allow the hardenedbone cement to support the spine adequately, because they make singlepoints of contact on each vertebral body surface (the equivalent of acircle inside a square, or a sphere inside a cylinder). The balloons ofthe present invention recreate the flat surfaces of the vertebral bodyby including restraints that keep the balloon in the desired shape. Thismaximizes the contacts between the vertebral body surfaces and the bonecement, which strengthens the spine. In addition, the volume of bonecement that fills these cavities creates a thick mantle of cement (4 mmor greater), which is required for appropriate compressive strength.Another useful feature, although not required, are ridges in theballoons which leave their imprint in the lining of compressedcancellous bone. The resulting bone cement “fingers” provide enhancedstability.

[0041] The balloons which optimally compress cancellous bone invertebral bodies are the balloons listed as balloon types 1, 2 and 3above. These balloons are configured to approximate the shape of thevertebral body. Since the balloon is chosen to occupy 70 to 90% of theinner volume, it will not exert undue pressure on the sides of thevertebral body, thus the vertebral body will not expand beyond itsnormal size (fractured or unfractured). However, since the balloon hasthe height of an unfractured vertebral body, it can move the top, whichhas collapsed, back to its original position.

[0042] One aspect of the invention provides a device for insertion intoa vertebral body to apply a force capable of compacting cancellous boneand moving fractured cortical bone. The device includes a catheterextending along an axis and having a distal end sized and configured forinsertion through a cannula into the vertebral body. The cathetercarries near its distal end an inflatable body having a wall sized andconfigured for passage within the cannula into the vertebral body whenthe inflatable body is in a collapsed condition. The wall is furthersized and configured to apply the in response to expansion of theinflatable body within the vertebral body. The wall includes, wheninflated, opposed side surfaces extending along an elongatedlongitudinal axis that is substantially aligned with the axis of thecatheter. The inflatable body has a height of approximately 0.5 cm to3.5 cm, an anterior to posterior dimension of approximately 0.5 cm to3.5 cm, and a side to side dimension of approximately 0.5 cm to 5.0 cm.

[0043] In a representative embodiment, the inflatable body comprises aballoon and the cannula is a percutaneious cannula.

[0044] In another aspect of the invention, the wall includes changes inwall thickness which restrain the opposed sided surfaces from expandingbeyond a substantially flat condition.

[0045] According to another aspect of the invention, the wall includesan internal restraint which restrains the opposed side surfaces fromexpanding beyond a substantially flat condition. The internal restraintmay include a mesh material, a string material, a woven material, aseam, or an essentially non-elastic material.

[0046] In yet another aspect of the invention, the wall includes anexternal restraint which restrains the opposed side surfaces fromexpanding beyond a substantially flat condition. The internal restraintmay include a mesh material, a string material, a woven material, aseam, or an essentially non-elastic material.

[0047] A primary goal of percutaneous proximal humeral augmentation isto create a cavity inside the proximal humerus whose configuration isoptimal for supporting the proximal humerus. Another important goal isto help realign the humeral head with the shaft of the humerus when theyare separated by a fracture. Both of these goals must be achieved byexerting pressure primarily on the cancellous bone, and not the corticalbone. Undue pressure against the cortical bone could conceivably cause aworsening of a shoulder fracture by causing cortical bone fractures.

[0048] The present invention satisfies these goals through the design ofthe inflatable devices to be described. Inflating such a devicecompresses the cancellous bone against the cortical walls of theepiphysis and metaphysis of the proximal humerus thereby creating acavity. In some cases, depending on the fracture location, the balloonor inflatable device may be used to extend the cavity into the proximalpart of the humeral diaphysis.

[0049] Due to the design of the “sphere on a stand” balloon (describedas number 7 above), the cavity made by this balloon recreates orapproximates the shape of the inside cortical wall of the proximalhumerus. The approximate volume of the cavity made by the “spherical ona stand balloon” is 70 to 90% that of the proximal humeral epiphysis andmetaphysis, primarily, but not necessarily exclusive of, part of thediaphysis. The shape approximates the shape of the humeral head. The“base” is designed to compress the trabecular bone into a “plug” of bonein the distal metaphysis or proximal diaphysis. This plug of bone willprevent the flow of injectable material into the shaft of the humerus,improving the clinical outcome. The sphere can also be used without abase.

[0050] A primary goal of percutaneous distal radius augmentation is tocreate a cavity inside the distal radius whose configuration is optimalfor supporting the distal radius. Another important goal is to help finetune fracture realignment after the fracture has been partiallyrealigned by finger traps. Both of these goals must be achieved byexerting pressure primarily on the cancellous bone and not on thecortical bone. Excessive pressure against the cortical bone couldconceivably cause cortical bone fractures, thus worsening the condition.

[0051] The present invention satisfies these goals through the design ofinflatable devices either already described or to be described.

[0052] The design of the “humpbacked banana”, or modified pyramid design(as described as number 5 above), approximates the shape of the distalradius and therefore, the cavity made by this balloon approximates theshape of the distal radius as well. The approximate volume of the cavityto be made by this humpbacked banana shaped balloon is 70 to 90% that ofthe distal radial epiphysis and metaphysis primarily of, but notnecessarily exclusive of, some part of the distal radial diaphysis.Inflating such a device compresses the cancellous bone against thecortical walls of the epiphysis and metaphysis of the distal radius inorder to create a cavity. In some cases, depending on the fracturelocation, the osseous balloon or inflatable device may be used to extendthe cavity into the distal part of the radial diaphysis.

[0053] A primary goal of percutaneous femoral head (or humeral head)augmentation is to create a cavity inside the femoral head (or humeralhead) whose configuration is optimal for supporting the femoral head.Another important goal is to help compress avascular (or aseptic)necrotic bone or support avascular necrotic bone is the femoral head.This goal may include the realignment of avascular bone back into theposition it previously occupied in the femoral head in order to improvethe spherical shape of the femoral head. These goals must be achieved byexerting pressure primarily on the cancellous bone inside the femoralhead.

[0054] The present invention satisfied these goals through the design ofinflatable devices either already described or to be described.

[0055] The design of the spherical osseous balloon (described as balloontype 4 above) approximates the shape of the femoral head and thereforecreates a cavity which approximates the shape of the femoral head aswell. (It should be noted that the spherical shape of this inflatabledevice also approximates the shape of the humeral head and would, infact, be appropriate for cavity formation in this osseous location aswell.) Inflating such a device compresses the cancellous bone of thefemoral head against its inner cortical walls in order to create acavity. In some cases, depending upon the extent of the avascularnecrosis, a smaller or larger cavity inside the femoral head will beformed. In some cases, if the area of avascular necrosis is small, asmall balloon will be utilized which might create a cavity only 10 to15% of the total volume of the femoral head. If larger areas of thefemoral head are involved with the avascular necrosis, then a largerballoon would be utilized which might create a much larger cavity,approaching 80 to 90% of the volume of the femoral head.

[0056] The hemispherical balloon approximates the shape of the top halfof the femoral (and humeral) head, and provides a means for compactingcancellous bone in an area of avascular necrosis or small fracturewithout disturbing the rest of the head. This makes it easier to do afuture total joint replacement if required.

[0057] A primary goal of percutaneous proximal tibial augmentation is tocreate a cavity inside the proximal tibia whose configuration is optimalfor supporting either the medial or lateral tibial plateaus. Anotherimportant goal is to help realign the fracture fragments of tibialplateau fractures, particularly those features with fragments depressedbelow (or inferior to) their usual location. Both of these objectivesmust be achieved by exerting pressure on primarily the cancellous boneand not the cortical bone. Pressure on the cortical bone couldconceivably cause worsening of the tibial plateau fracture.

[0058] The present invention satisfies these goals through the design ofthe inflatable devices to be described. Inflating such a devicecompresses the cancellous bone against the cortical walls of the medialor lateral tibial plateau in order to create a cavity.

[0059] Due to the design of the “elliptical cylinder” balloon (describedas balloon type 6 above) the cavity made by this balloon recreates orapproximates the shape of the cortical walls of either the medial orlateral tibial plateaus. The approximate volume of the cavity to be madeby the appropriate elliptical cylindrical balloon is 50 to 90% of theproximal epiphyseal bone of either the medial half or the lateral halfof the tibial.

[0060] According to one aspect of the invention, a system for treating abone having an interior volume occupied, at least in part, by cancellousbone comprises a first tool, a second tool, and a third tool. The bonemay be e.g., a vertebral body. The first tool establishes a percutaneousaccess path to bone. The second tool is sized and configured to beintroduced through the percutaneous access path to form a void thatoccupies less than the interior volume. The third tool places within thevoid through the percutaneous access path a volume of filling material.

[0061] In one embodiment, the interior volume has a maximumanterior-to-posterior dimension and the void has a dimension, measuredin an anterior-to-posterior direction, that is less than the maximumanterior-to-posterior dimension of the interior volume.

[0062] In one embodiment, the interior volume has a maximum side-to-sidedimension and the void has a dimension, measured in a side-to-sidedirection, that is less than the maximum side-to-side dimension of theinterior volume.

[0063] Another aspect of the invention provides a method of treating abone having an interior volume occupied, at least in part, by cancellousbone. The bone may be, e.g., a vertebral body. The method providesestablishing a percutaneous access path to bone. A tool is introducedthrough the percutaneous access path and manipulated to form a void thatoccupies less than the interior volume. A volume of filling material isthen placed within the void through the percutaneous access path.

[0064] In one embodiment, the interior volume has a maximumanterior-to-posterior dimension and the void has a dimension, measuredin an anterior-to-posterior direction, that is less than the maximumanterior-to-posterior dimension of the interior volume.

[0065] In one embodiment, the interior volume has a maximum side-to-sidedimension and the void has a dimension, measured in a side-to-sidedirection, that is less than the maximum side-to-side dimension of theinterior volume.

[0066] Other objects of the present invention will become apparent asthe following specification progresses, reference being had to theaccompanying drawings for an illustration of the invention.

DESCRIPTION OF THE DRAWINGS

[0067]FIG. 1 is a perspective view of a first embodiment of the balloonof the present invention, the embodiment being in the shape of a stackeddoughnut assembly.

[0068]FIG. 2 is a vertical section through the balloon of FIG. 1 showingthe way in which the doughnut portions of the balloon of FIG. 1, fitinto a cavity of a vertebral body.

[0069]FIG. 3 is a schematic view of another embodiment of the balloon ofthe present invention showing three stacked balloons and string-likerestraints for limiting the expansion of the balloon in directions ofinflation.

[0070]FIG. 4 is a top plan view of a spherical balloon having acylindrical ring surrounding the balloon.

[0071]FIG. 5 is a vertical section through the spherical balloon andring of FIG. 4.

[0072]FIG. 6 shows an oblong-shaped balloon with a catheter extendinginto the central portion of the balloon.

[0073]FIG. 6A is a perspective view of the way in which a catheter isarranged relative to the inner tubes for inflating the balloon of FIG.6.

[0074]FIG. 7 is a suction tube and a contrast injection tube forcarrying out the inflation of the balloon and removal of debris causedby expansion from the balloon itself.

[0075]FIG. 8 is a vertical section through a balloon after it has beendeflated and as it is being inserted into the vertebral body of a human.

[0076]FIGS. 9 and 9A are side elevational views of a cannula showing howthe protective sleeve or guard member expands when leaving the cannula.

[0077]FIG. 9B is a vertical section through a vertebral bone into whichan access hole has been drilled.

[0078]FIG. 10 is a perspective view of another embodiment of the balloonof the present invention formed in the shape of a kidney bean.

[0079]FIG. 11 is a perspective view of the vertebral bone showing thekidney shaped balloon of FIG. 10 inserted in the bone and expanded.

[0080]FIG. 12 is a top view of a kidney shaped balloon formed of severalcompartments by a heating element or branding tool.

[0081]FIG. 13 is a cross-sectional view taken along line 13-13 of FIG.12 but with two kidney shaped balloons that have been stacked.

[0082]FIG. 14 is a view similar to FIG. 11 but showing the stackedkidney shaped balloon of FIG. 13 in the vertebral bone.

[0083]FIG. 15 is a top view of a kidney balloon showing outer tuftsholding inner strings in place interconnecting the top and bottom wallsof the balloon.

[0084]FIG. 16 is a cross sectional view taken along lines 16-16 of FIG.15.

[0085]FIG. 17A is a dorsal view of a humpback banana balloon in a rightdistal radius.

[0086]FIG. 17B is a cross sectional view of FIG. 17A taken along line17B-17B of FIG. 17A.

[0087]FIG. 18 is a spherical balloon with a base in a proximal humerusviewed from the front (anterior) of the left proximal humerus.

[0088]FIG. 19A is the front (anterior) view of the proximal tibia withthe elliptical cylinder balloon introduced beneath the medial tibialplateau.

[0089]FIG. 19B is a three quarter view of the balloon of FIG. 19A.

[0090]FIG. 19C is a side elevational view of the balloon of FIG. 19A.

[0091]FIG. 19D is a top plan view of the balloon of FIG. 19A.

[0092]FIG. 20 is a spherically shaped balloon for treating avascularnecrosis of the head of the femur (or humerus) as seen from the front(anterior) of the left hip.

[0093]FIG. 20A is a side view of a hemispherically shaped balloon fortreating avascular necrosis of the head of the femur (or humerus).

DETAILED DESCRIPTION Balloons for Vertebral Bodies

[0094] A first embodiment of the balloon (FIG. 1) of the presentinvention is broadly denoted by the numeral 10 and includes a balloonbody 11 having a pair of hollow, inflatable, non-expandable parts 12 and14 of flexible material, such as PET or Kevlar. Parts 12 and 14 have asuction tube 16 therebetween for drawing fats and other debris bysuction into tube 16 for transfer to a remote disposal location.Catheter 16 has one or more suction holes so that suction may be appliedto the open end of tube 16 from a suction source (not shown).

[0095] The parts 12 and 14 are connected together by an adhesive whichcan be of any suitable type. Parts 12 and 14 are doughnut-shaped asshown in FIG. 1 and have tubes 18 and 20 which communicate with andextend away from the parts 12 and 14, respectively, to a source ofinflating liquid under pressure (not shown). The liquid can be anysterile biocompatible solution. The liquid inflates the balloon 10,particularly parts 12 and 14 thereof after the balloon has been insertedin a collapsed condition (FIG. 8) into a bone to be treated, such as avertebral bone 22 in FIG. 2. The above-mentioned U.S. Pat. Nos.4,969,888 and 5,108,404 disclose the use of a guide pin and cannula forinserting the balloon into bone to be treated when the balloon isdeflated and has been inserted into a tube and driven by the catheterinto the cortical bone where the balloon is inflated.

[0096]FIG. 8 shows a deflated balloon 10 being inserted through acannula 26 into bone. The balloon in cannula 26 is deflated and isforced through the cannula by exerting manual force on the catheter 21which extends into a passage 28 extending into the interior of the bone.The catheter is slightly flexible but is sufficiently rigid to allow theballoon to be forced into the interior of the bone where the balloon isthen inflated by directing fluid into tube 88 whose outlet ends arecoupled to respective parts 12 and 14.

[0097] In use, balloon 10 is initially deflated and, after the bone tobe filled with the balloon has been prepared to receive the balloon withdrilling, the deflated balloon is forced into the bone in a collapsedcondition through cannula 26. The bone is shown in FIG. 2. The balloonis oriented preferably in the bone such that it allows minimum pressureto be exerted on the bone marrow and/or cancellous bone if there is nofracture or collapse of the bone. Such pressure will compress the bonemarrow and/or cancellous bone against the inner wall of the corticalbone, thereby compacting the bone marrow of the bone to be treated andto further enlarge the cavity in which the bone marrow is to be replacedby a biocompatible, flowable bone material.

[0098] The balloon is then inflated to compact the bone marrow and/orcancellous bone in the cavity and, after compaction of the bone marrowand/or cancellous bone, the balloon is deflated and removed from thecavity. While inflation of the balloon and compaction occurs, fats andother debris are sucked out of the space between and around parts 12 and14 by applying a suction force to catheter tube 16. Following this, andfollowing the compaction of the bone marrow, the balloon is deflated andpulled out of the cavity by applying a manual pulling force to thecatheter tube 21.

[0099] The second embodiment of the inflatable device of the presentinvention is broadly denoted by the numeral 60 and is shown in FIGS. 4and 5. Balloon 60 includes a central spherical part 62 which is hollowand which receives an inflating liquid under pressure through a tube 64.The spherical part is provided with a spherical outer surface 66 and hasan outer periphery which is surrounded substantially by a ring shapedpart 68 having tube segments 70 for inflation of part 68. A pair ofpassages 69 interconnect parts 62 and 68. A suction tube segment 72draws liquid and debris from the bone cavity being formed by the balloon60.

[0100] Provision can be made for a balloon sleeve 71 for balloon 60 andfor all balloons disclosed herein. A balloon sleeve 71 (FIG. 9) isshiftably mounted in an outer tube 71 a and can be used to insert theballoon 60 when deflated into a cortical bone. The sleeve 71 hasresilient fingers 71 b which bear against the interior of the entranceopening 71 c of the vertebral bone 22 (FIG. 9A) to prevent tearing ofthe balloon. Upon removal of the balloon sleeve, liquid under pressurewill be directed into tube 64 which will inflate parts 62 and 68 so asto compact the bone marrow within the cortical bone. Following this,balloon 60 is deflated and removed from the bone cavity.

[0101]FIGS. 6 and 6A show several views of a modified doughnut shapeballoon 80 of the type shown in FIGS. 1 and 2, except the doughnutshapes of balloon 80 are not stitched onto one another. In FIG. 6,balloon 80 has a pear-shaped outer convex surface 82 which is made up ofa first hollow part 84 and a second hollow part 85. A tube 88 isprovided for directing liquid into the two parts along branches 90 and92 to inflate the parts after the parts have been inserted into themedullary cavity of a bone. A catheter tube 16 is inserted into thespace 96 between two parts of the balloon 80. An adhesive bonds the twoparts 84 and 85 together at the interface thereof.

[0102]FIG. 6A shows the way in which the catheter tube 16 is insertedinto the space or opening 96 between the two parts of the balloon 80.

[0103]FIG. 7 shows tube 88 of which, after directing inflating liquidinto the balloon 80, can inject contrast material into the balloon 80 sothat x-rays can be taken of the balloon with the inflating materialtherewithin to determine the proper placement of the balloon. Tube 16 isalso shown in FIG. 6, it being attached in some suitable manner to theouter side wall surface of tube 88.

[0104] Still another embodiment of the invention is shown in FIG. 3which is similar to FIG. 1 except that it is round and not a doughnutand includes an inflatable device 109 having three balloon units 110,112 and 114 which are inflatable and which have string-like restraints117 which limit the expansion of the balloon units in a directiontransverse to the longitudinal axes of the balloon units. The restraintsare made of the same or similar material as that of the balloon so thatthey have some resilience but substantially no expansion capability.

[0105] A tube system 115 is provided to direct liquid under pressureinto balloon units 110, 112 and 114 so that liquid can be used toinflate the balloon units when placed inside the bone in a deflatedstate. Following the proper inflation and compaction of the bone marrow,the balloon can be removed by deflating it and pulling it outwardly ofthe bone being treated. The restraints keep the opposed sides 77 and 79substantially flat and parallel with each other.

[0106] In FIG. 10, another embodiment of the inflatable balloon isshown. The device is a kidney shaped balloon body 130 having a pair ofopposed kidney shaped side walls 132 which are adapted to be collapsedand to cooperate with a continuous end wall 134 so that the balloon 130can be forced into a bone 136 shown in FIG. 11. A tube 138 is used todirect inflating liquid into the balloon to inflate the balloon andcause it to assume the dimensions and location shown vertebral body 136in FIG. 11. Device 130 will compress the cancellous bone if there is nofracture or collapse of the cancellous bone. The restraints for thisaction are due to the side and end walls of the balloon.

[0107]FIG. 12 shows a balloon 140 which is also kidney shaped and has atube 142 for directing an inflatable liquid into the tube for inflatingthe balloon. The balloon is initially a single chamber bladder but thebladder can be branded along curved lines or strips 141 to formattachment lines 144 which take the shape of side-by-side compartments146 which are kidney shaped as shown in FIG. 13. The branding causes awelding of the two sides of the bladder to occur since the material isstandard medical balloon material, which is similar to plastic and canbe formed by heat.

[0108]FIG. 14 is a perspective view of a vertebral body 147 containingthe balloon of FIG. 12, showing a double stacked balloon 140 when it isinserted in vertebral bone 147.

[0109]FIG. 15 is a view similar to FIG. 10 except that tufts 155, whichare string-like restraints, extend between and are connected to the sidewalls 152 of inflatable device 150 and limit the expansion of the sidewalls with respect to each other, thus rendering the side wallsgenerally parallel with each other. Tube 88 is used to fill the kidneyshaped balloon with an inflating liquid in the manner described above.

[0110] The dimensions for the vertebral body balloon will vary across abroad range. The heights (H, FIG. 11) of the vertebral body balloon forboth lumbar and thoracic vertebral bodies typically range from 0.5 cm to3.5 cm. The anterior to posterior (A, FIG. 11) vertebral body balloondimensions for both lumbar and thoracic vertebral bodies range from 0.5cm to 3.5 cm. The side to side (L, FIG. 11) vertebral body dimensionsfor thoracic vertebral bodies will range from 0.5 cm to 3.5 cm. The sideto side vertebral body dimensions for lumbar vertebral bodies will rangefrom 0.5 cm to 5.0 cm.

[0111] The eventual selection of the appropriate balloon for, forinstance, a given vertebral body is based upon several factors. Theanterior-posterior (A-P) balloon dimension for a given vertebral body isselected from the CT scan or plain film x-ray views of the vertebralbody. The A-P dimension is measured from the internal cortical wall ofthe anterior cortex to the internal cortical wall of the posteriorcortex of the vertebral body. In general, the appropriate A-P balloondimension is 5 to 7 millimeters less than this measurement.

[0112] The appropriate side to side balloon dimensions for a givenvertebral body is selected from the CT scan or from a plain film x-rayview of the vertebral body to be treated. The side to side distance ismeasured from the internal cortical walls of the side of the vertebralbone. In general, the appropriate side to side balloon dimension is 5 to7 millimeters less than this measurement by the addition of the lumbarvertebral body tends to be much wider than side to side dimension thentheir A-P dimension. In thoracic vertebral bodies, the side to sidedimension and their A-P dimensions are almost equal.

[0113] The height dimensions of the appropriate vertebral body balloonfor a given vertebral body is chosen by the CT scan or x-ray views ofthe vertebral bodies above and below the vertebral body to be treated.The height of the vertebral bodies above and below the vertebral body tobe treated are measured and averaged. This average is used to determinethe appropriate height dimension of the chosen vertebral body balloon.

Balloons for Long Bones

[0114] Long bones which can be treated with the use of balloons of thepresent invention include distal radius (larger arm bone at the wrist),proximal tibial plateau (leg bone just below the knee), proximal humerus(upper end of the arm at the shoulder), and proximal femoral head (legbone in the hip).

Distal Radius Balloon

[0115] For the distal radius, a balloon 160 is shown in the distalradius 152 and the balloon has a shape which approximates a pyramid butmore closely can be considered the shape of a humpbacked banana in thatit substantially fills the interior of the space of the distal radius toforce cancellous bone 154 lightly against the inner surface 156 ofcortical bone 158.

[0116] The balloon 160 has a lower, conical portion 159 which extendsdownwardly into the hollow space of the distal radius 152, and thisconical portion 159 increases in cross section as a central distalportion 161 is approached. The cross section of the balloon 160 is shownat a central location (FIG. 17B) and this location is near the widestlocation of the balloon. The upper end of the balloon, denoted by thenumeral 162, converges to the catheter 88 for directing a liquid intothe balloon for inflating the same to force the cancellous bone againstthe inner surface of the cortical bone. The shape of the balloon 160 isdetermined and restrained by tufts formed by string restraints 165.These restraints are optional and provide additional strength to theballoon body 160, but are not required to achieve the desiredconfiguration. The balloon is placed into and taken out of the distalradius in the same manner as that described above with respect to thevertebral bone.

[0117] The dimensions of the distal radius balloon vary as follows:

[0118] The proximal end of the balloon (i.e. the part nearest the elbow)is cylindrical in shape and will vary from 0.5.times.0.5 cm to1.8.times.1.8 cm.

[0119] The length of the distal radius balloon will vary from 1.0 cm to12.0 cm.

[0120] The widest medial to lateral dimension of the distal radiusballoon, which occurs at or near the distal radio-ulnar joint, willmeasure from 1.0 cm to 2.5 cm.

[0121] The distal anterior-posterior dimension of the distal radiusballoon will vary from 0.5 to 3.0 cm.

Proximal Humerus Fracture Balloon

[0122] The selection of the appropriate balloon size to treat a givenfracture of the distal radius will depend on the radiological size ofthe distal radius and the location of the fracture.

[0123] In the case of the proximal humerus 169, a balloon 166 shown inFIG. 18 is spherical and has a base design. It compacts the cancellousbone 168 in a proximal humerus 169. A mesh 170, embedded or laminatedand/or winding, may be used to form a neck 172 on the balloon 166, andsecond mesh 170 a may be used to conform the bottom of the base 172 a tothe shape of the inner cortical wall at the start of the shaft. Theserestraints provide additional strength to the balloon body, but theconfiguration can be achieved through molding of the balloon body. Thisis so that the cancellous bone will be as shown in the compacted regionsurrounding the balloon 166 as shown in FIG. 18. The cortical bone 173is relatively wide at the base 174 and is thin-walled at the upper end175. The balloon 166 has a feed tube 177 into which liquid underpressure is forced into the balloon to inflate it to lightly compact thecancellous bone in the proximal humerus. The balloon is inserted intoand taken out of the proximal humerus in the same manner as thatdescribed above with respect to the vertebral bone.

[0124] The dimensions of the proximal humerus fracture balloon vary asfollows:

[0125] The spherical end of the balloon will vary from 1.0.times.1.0 cmto 3.0.times.3.0 cm.

[0126] The neck of the proximal humeral fracture balloon will vary from0.8.times.0.8 cm to 3.0.times.3.0 cm.

[0127] The width of the base portion or distal portion of the proximalnumeral fracture balloon will vary from 0.5.times.0.5 cm to2.5.times.2.5 cm.

[0128] The length of the balloon will vary from 4.0 cm to 14.0 cm.

[0129] The selection of the appropriate balloon to treat a givenproximal humeral fracture depends on the radiologic size of the proximalhumerus and the location of the fracture.

Proximal Tibial Plateau Fracture Balloon

[0130] The tibial fracture is shown in FIG. 19A in which a balloon 180is placed in one side 182 of a tibia 183. The balloon, when inflated,compacts the cancellous bone in the layer 184 surrounding the balloon180. A cross section of the balloon is shown in FIG. 19C wherein theballoon has a pair of opposed sides 185 and 187 which are interconnectedby restraints 188 which can be in the form of strings or flexiblemembers of any suitable construction. The main purpose of the restraintsis to make the sides 185 and 187 substantially parallel with each otherand non-spherical. A tube 190 is coupled to the balloon 180 to directliquid into and out of the balloon. The ends of the restraints are shownin FIGS. 19B and 19D and denoted by the numeral 191. The balloon isinserted into and taken out of the tibia in the same manner as thatdescribed above with respect to the vertebral bone. FIG. 19B shows asubstantially circular configuration for the balloon; whereas, FIG. 19Dshows a substantially elliptical version of the balloon.

[0131] The dimensions of the proximal tibial plateau fracture balloonvary as follows:

[0132] The thickness or height of the balloon will vary from 0.5 cm to5.0 cm.

[0133] The anterior/posterior (front to back) dimension will vary from1.0 cm to 6.0 cm.

[0134] The side to side (medial to lateral) dimension will vary from 1.0cm to 6.0 cm.

[0135] The selection of the appropriate balloon to treat a given tibialplateau fracture will depend on the radiological size of the proximaltibial and the location of the fracture.

Femoral Head Balloon

[0136] In the case of the femoral head, a balloon 200 is shown as havingbeen inserted inside the cortical bone 202 of the femoral head which isthin at the outer end 204 of the femur and which can increase inthickness at the lower end 206 of the femur. The cortical bone surroundsthe cancellous bone 207 and this bone is compacted by the inflation ofballoon 200. The tube for directing liquid for inflation purposes intothe balloon is denoted by the numeral 209. It extends along the femoralneck and is directed into the femoral head which is generally sphericalin configuration. FIG. 20A shows that the balloon, denoted by thenumeral 200 a, can be hemispherical as well as spherical, as shown inFIG. 20.

[0137] The balloon 200 is inserted into and taken out of the femoralhead in the same manner as that described with respect to the vertebralbone. The hemispherical shape is maintained in this example by bondingoverlapping portions of the bottom, creating pleats 200 b as shown inFIG. 20A.

[0138] The dimensions of the femoral head balloon vary as follows:

[0139] The diameter of the femoral head balloon will vary from 1.0 cm toup to 4.5 cm. The appropriate size of the femoral head balloon to bechosen depends on the radiological or CT scan size of the head of thefemur and the location and size of the avascular necrotic bone. Thedimensions of the hemispherical balloon are the same as the those of thespherical balloon, except that approximately one half is provided.

What is claimed is:
 1. A method of treating a bone having an interiorvolume occupied, at least in part, by cancellous bone comprisingestablishing a percutaneous access path to bone, introducing a toolthrough the percutaneous access path, manipulating the tool to form avoid that occupies less than the interior volume, and placing within thevoid through the percutaneous access path a volume of filling material.2. A method according to claim 1 wherein the tool is manipulated to forma void that occupies less than about 90% of the interior volume.
 3. Amethod according to claim 1 wherein the tool is manipulated to form avoid that occupies about 10% to about 90% of the interior volume.
 4. Amethod according to claim 1 wherein the tool is manipulated to form avoid that occupies about 40% to about 90% of the interior volume.
 5. Amethod according to claim 1 wherein the tool is manipulated to form avoid that occupies about 70% to about 90% of the interior volume.
 6. Amethod according to claim 1 further including selecting a vertebral bodyto be the bone to be treated.
 7. A method of treating a bone having aninterior volume with a maximum anterior-to-posterior dimension occupied,at least in part, by cancellous bone comprising establishing apercutaneous access path to bone, introducing a tool through thepercutaneous access path, manipulating the tool to form a void having adimension, measured in an anterior-to-posterior direction, that is lessthan the maximum anterior-to-posterior dimension of the interior volume,and placing within the void through the percutaneous access path avolume of filling material.
 8. A method according to claim 7 wherein thetool is manipulated to form a void having a dimension, measured in ananterior-to-posterior direction, that is at least about 5 mm less thanthe maximum anterior-to-posterior dimension of the interior volume.
 9. Amethod according to claim 7 wherein the tool is manipulated to form avoid having a dimension, measured in an anterior-to-posterior direction,that is about 5 mm to about 7 mm less than the maximumanterior-to-posterior dimension of the interior volume.
 10. A methodaccording to claim 7 wherein the tool is manipulated to form a void thatoccupies less than about 90% of the interior volume.
 11. A methodaccording to claim 7 wherein the tool is manipulated to form a void thatoccupies about 10% to about 90% of the interior volume.
 12. A methodaccording to claim 7 wherein the tool is manipulated to form a void thatoccupies about 40% to about 90% of the interior volume.
 13. A methodaccording to claim 7 wherein the tool is manipulated to form a void thatoccupies about 70% to about 90% of the interior volume.
 14. A methodaccording to claim 7 further including selecting a vertebral body to bethe bone to be treated.
 15. A method of treating a bone having aninterior volume with a maximum side-to-side dimension occupied, at leastin part, by cancellous bone comprising establishing a percutaneousaccess path to bone, introducing a tool through the percutaneous accesspath, manipulating the tool to form a void having a dimension, measuredin a side-to-side direction, that is less than the maximum side-to-sidedimension of the interior volume, and placing within the void throughthe percutaneous access path a volume of filling material.
 16. A methodaccording to claim 15 wherein the tool is manipulated to form a voidhaving a dimension, measured in a side-to-side direction, that is atleast about 5 mm less than the maximum side-to-side dimension of theinterior volume.
 17. A method according to claim 15 wherein the tool ismanipulated to form a void having a dimension, measured in aside-to-side direction, that is about 5 mm to about 7 mm less than themaximum side-to-side dimension of the interior volume.
 18. A methodaccording to claim 15 wherein the tool is manipulated to form a voidthat occupies less than about 90% of the interior volume.
 19. A methodaccording to claim 15 wherein the tool is manipulated to form a voidthat occupies about 10% to about 90% of the interior volume.
 20. Amethod according to claim 15 wherein the tool is manipulated to form avoid that occupies about 40% to about 90% of the interior volume.
 21. Amethod according to claim 15 wherein the tool is manipulated to form avoid that occupies about 70% to about 90% of the interior volume.
 22. Amethod according to claim 15 further including selecting a vertebralbody to be the bone to be treated.
 23. A method for treating a bonehaving an interior volume with a maximum anterior-to-posterior dimensionand a maximum side-to-side dimension occupied, at least in part, bycancellous bone comprising establishing a percutaneous access path tobone, introducing a tool through the percutaneous access path,manipulating the tool to form a void having a dimension, measured in ananterior-to-posterior direction, that is less than the maximumanterior-to-posterior dimension of the interior volume and a dimension,measured in a side-to-side direction, that is less than the maximumside-to-side dimension of the interior volume, and placing within thevoid through the percutaneous access path a volume of filling material.24. A method according to claim 23 wherein the tool is manipulated toform a void that occupies less than about 90% of the interior volume.25. A method according to claim 23 wherein the tool is manipulated toform a void that occupies about 10% to about 90% of the interior volume.26. A method according to claim 23 wherein the tool is manipulated toform a void that occupies about 40% to about 90% of the interior volume.27. A method according to claim 23 wherein the tool is manipulated toform a void that occupies about 70% to about 90% of the interior volume.28. A method according to claim 23 wherein the tool is manipulated toform a void having a dimension, measured in an anterior-to-posteriordirection, that is at least about 5 mm less than the maximumanterior-to-posterior dimension of the interior volume.
 29. A methodaccording to claim 23 wherein the tool is manipulated to form a voidhaving a dimension, measured in an anterior-to-posterior direction, thatis about 5 mm to about 7 mm less than the maximum anterior-to-posteriordimension of the interior volume.
 30. A method according to claim 28 or29 wherein the tool is manipulated to form a void having a dimension,measured in a side-to-side direction, that is at least about 5 mm lessthan the maximum side-to-side dimension of the interior volume.
 31. Amethod according to claim 28 or 29 wherein the tool is manipulated toform a void having a dimension, measured in a side-to-side direction,that is about 5 mm to about 7 mm less than the maximum side-to-sidedimension of the interior volume.
 32. A method according to claim 23wherein the tool is manipulated to form a void having a dimension,measured in a side-to-side direction, that is at least about 5 mm lessthan the maximum side-to-side dimension of the interior volume.
 33. Amethod according to claim 23 wherein the tool is manipulated to form avoid having a dimension, measured in a side-to-side direction, that isabout 5 mm to about 7 mm less than the maximum side-to-side dimension ofthe interior volume.
 34. A method according to claim 23 furtherincluding selecting a vertebral body to be the bone to be treated.
 35. Amethod according to claim 1 or 7 or 15 or 23 wherein the tool isintroduced carried by an elongate member.
 36. A method according toclaim 35 wherein the elongate member comprises a catheter.
 37. A methodaccording to claim 1 or 7 or 15 or 23 wherein the tool is manipulated tocompact cancellous bone.
 38. A method according to claim 37 wherein thetool, when manipulated to compact cancellous bone, forms a shell aboutthe void.
 39. A method according to claim 1 or 7 or 15 or 23 wherein thetool is manipulated to lift fractured cortical bone.
 40. A methodaccording to claim 1 or 7 or 15 or 23 wherein the tool is manipulated toreduce a cortical bone fracture.
 41. A method according to claim 1 or 7or 15 or 23 wherein the tool is manipulated to move fractured corticalbone towards a natural anatomic position.
 42. A method according toclaim 1 or 7 or 15 or 23 wherein the tool comprises a body that, whenmanipulated, expands.
 43. A method according to claim 42 wherein theexpansion is due to inflation of the body.
 44. A method according toclaim 1 or 7 or 15 or 23 wherein the tool comprises a balloon that, whenmanipulated, is inflated.
 45. A method according to claim 1 or 7 or 15or 23 wherein the tool, when manipulated, assumes a non-spherical shape.46. A method according to claim 1 or 7 or 15 or 23 wherein, aftermanipulation to form the void, the tool is withdrawn from bone.
 47. Amethod according to claim 1 or 7 or 15 or 23 wherein the fillermaterial, when placed in the void, imparts compressive strength.